Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.

Coherent-potential-approximation calculations for Pd H x

Abstract: The angular-momentum components of the density of states (DOS) for substoichiometric $\mathrm{Pd}{\mathrm{H}}_{x}$ were calculated by the coherent-potential approximation (CPA). A tight-binding form of the CPA was used, based on a Slater-Koster fit to first-principles APW calculations. The CPA DOS's have been used to calculate the electron-phonon interaction and superconducting transition temperatures as a function of hydrogen concentration $x$. The results are in good agreement with experiment and with previous calculations in which the rigid-band model was utilized. The CPA results for the electronic-specific-heat coefficient as a function of $x$ are in excellent agreement with experiment while the results of the rigid-band model are not.

First-principles study of ordering properties of substitutional alloys using the generalized perturbation method.

Abstract: Ab initio calculations of effective cluster interactions which make up the ordering energy of a substitutional alloy are reported. Tendencies toward ordering or phase separation and more generally phase stability in PdV and PdRh substitutional alloys are discussed. The study is based on an extension of the generalized perturbation method to systems describable by muffin-tin Hamiltonians in the framework of the multiple-scattering formalism in conjunction with the Korringa-Kohn-Rostoker coherent potential approximation. Future applications of the method are discussed.

Iron-based Heusler compounds Fe2YZ: Comparison with theoretical predictions of the crystal structure and magnetic properties

Abstract: The present work reports on the new soft ferromagnetic Heusler phases Fe${}_{2}$NiGe, Fe${}_{2}$CuGa, and Fe${}_{2}$CuAl, which in previous theoretical studies have been predicted to exist in a tetragonal Heusler structure. Together with the known phases Fe${}_{2}$CoGe and Fe${}_{2}$NiGa these materials have been synthesized and characterized by powder x-ray diffraction, ${}^{57}$Fe M\"ossbauer spectroscopy, superconducting quantum interference device, and energy-dispersive x-ray measurements. In particular M\"ossbauer spectroscopy was used to monitor the degree of local atomic order/disorder and to estimate magnetic moments at the Fe sites from the hyperfine fields. It is shown that in contrast to the previous predictions all the materials except Fe${}_{2}$NiGa basically adopt the inverse cubic Heusler ($X$) structure with differing degrees of disorder. The experimental data are compared with results from ab initio electronic structure calculations on local-density approximation level incorporating the effects of atomic disorder by using the coherent potential approximation. A good agreement between calculated and experimental magnetic moments is found for the cubic inverse Heusler phases. Model calculations on various atomic configurations demonstrate that antisite disorder tends to enhance the stability of the $X$ structure.

Impurities in a Biased Graphene Bilayer

Abstract: erties of the BGB it is important to understand the effects of the unavoidable disorder. In this letter we show that bound states exist for arbitrary weak impurity potentials, and that their properties, such as binding energies and localization lengths, can be externally controlled with a gate bias. Moreover, we obtain the wave-functions of the mid-gap states, from which we derive a simple criterion for when the overlap between wavefunctions becomes important. This overlap results in band gap renormalization and possibly band tails extending into the gap region, as in the case of ordinary heavily doped semiconductors [17], or impurity bands for deep impurities. Unlike ordinary semiconductors, the electronic density of states can be completely controlled via the electric field effect. The impurity interaction problem is studied within the coherent potential approximation (CPA). The Model. The low-energy effective bilayer Hamiltonian has the form [12, 13] (we use units such that ¯